Southern Cross Medical Library

The purpose of the Southern Cross Medical Library is to provide information of a general nature to help you better understand certain medical conditions. Always seek specific medical advice for treatment appropriate to you. This information is not intended to relate specifically to insurance or healthcare services provided by Southern Cross. For more articles go to the Medical Library index page.

Cold sores - symptoms and treatment

Cold sores are small fluid-filled blisters that typically develop on and around the lips. After the blisters break, a crust forms over the resulting sore. Cold sores usually heal in two to four weeks without leaving a scar. Although there is no cure, treatment with certain medications can help cold sores heal more quickly.

Causes

Cold sores are caused by certain strains of the herpes simplex virus (HSV). HSV type-1 is the strain that usually causes cold sores and is closely related to HSV type-2, which is the strain that usually causes genital herpes. However, either strain of HSV can cause blisters on and around the mouth or on the genitals.

They are most contagious when fluid is seeping from the blisters, but the virus can be transmitted to another person even when the blisters are too small to see. Transmission occurs through close contact, including kissing and sharing of eating utensils, razors, and towels. Also, oral sex can spread HSV type-1 to the genitals and HSV type-2 to the lips.

Most people are first exposed to the virus at a young age after close contact with a person who has a cold sore. The infection is permanent. Following the first episode of herpes infection, the virus lies inactive (dormant) inside nerves in the skin. It causes no symptoms most of the time but in some people the virus is periodically reactivated, and a cold sore re-emerges.

Cold sore recurrences can be triggered by:

Viral infection or fever (which is why cold sores are also known as ‘fever blisters’)

Cold sores tend to appear in the same place every time because the virus lies dormant in the nerves that lead to that spot on the skin.

Complications

The cold sore-causing HSV can cause problems in areas of the body other than the mouth, including:

Fingertips: HSV can be spread to the fingers. For example, children who suck their thumbs may transfer the infection from their mouths to their thumbs

Eyes: HSV can cause eye infections. Repeated eye infections can lead to scarring and injury, and possibly vision problems or blindness

Widespread areas of skin: People with eczema , which is an inflammatory skin condition, are at higher risk of cold sores spreading over their bodies

Other organs: In people with weakened immune systems, HSV can also affect the spinal cord, brain, and other organs.

People who have weakened immune systems due to other medical conditions or medical treatments are at higher risk of complications from HSV. Medical conditions and treatments that increase the risk of complications include:

HIV/AIDS

Severe burns

Cancer chemotherapy

Drugs used to prevent rejection of organ transplants.

Signs and symptoms

Cold sore signs and symptoms vary depending on whether it is a first outbreak or a recurrence, and typically can last several days. The blisters can take two to four weeks to heal completely. The signs and symptoms of cold sore recurrences tend to be less severe than the initial outbreak.

A cold sore episode usually passes through several symptom stages during a two- or three-day period:

Burning or tingling and itching around the lips for a day or so before blisters appear

Small fluid-filled blisters breakout along the border where the edge of the lips meets the skin of the face. Less commonly, cold sores occur around the nose or on the cheeks

The blisters burst, leaving shallow open sores that ooze fluid and then crust over into a scab.

Diagnosis

Your GP can usually diagnose cold sores by looking at them. They may take a sample from the blister for testing in a laboratory to confirm the diagnosis.

Treatment

Although cold sores generally clear up without treatment, several types of prescription or pharmacy-only antiviral drugs may speed the healing process.

Topical antiviral creams are available from pharmacies. They must be applied to the cold sore several times per day and work best if they are applied as soon as you recognise the early tingling feeling.

Oral antiviral medications in tablet form are available on prescription. In general, the tablets work better than the creams. Antiviral tablets are typically prescribed when a cold sore is very large, painful, or keeps coming back. For particularly severe infections, some antiviral drugs can be given with an injection.

The following home remedies may help to reduce the discomfort of a cold sore:

Applying over-the-counter topical preparations that contain a drying agent, such as alcohol, may speed healing

Applying a moisturising cream to soothe lips that have become dry

Applying ice at the first sign of tingling may help shorten the duration of the sore or prevent it from becoming a full-blown cold sore

Applying over-the-counter pain-relieving creams, such as those containing lidocaine or benzocaine, may provide some pain relief.

You should see a GP if a cold sore hasn't started to heal within 10 days, the cold sore is very large or painful, you or your child also have swollen, painful gums and sores in the mouth, you're pregnant, or you have a weakened immune system.

A pharmacist can recommend creams to ease pain and irritation, antiviral creams to speed up healing time, and cold sore patches to protect the skin while it heals.

Prevention

An antiviral medication to be taken on a regular basis may be prescribed for people who get frequent recurrences of cold sores or who are at high risk of complications.

If sunlight seems to trigger recurrences, regular application of lip balms containing sunblock or zinc oxide cream to protect your lips from the sun may help to prevent an outbreak.

When you have cold sore blisters, taking the following precautions may help prevent spreading cold sores to other people or to other parts of your body: